Abstract: A small center distance is provided between a crankshaft and a gearshift shaft disposed in parallel. A power unit is built compactly in a direction of arrangement of the crankshaft and the gearshift shaft for supporting reliably the gearshift shaft on which heavy, first and second gearshift clutches are supported. A transmission includes a main shaft, disposed in parallel with a crankshaft and rotatably supported in a crankcase, and first and second gearshift clutches. The first and second gearshift clutches change a gearshift position in a first gearshift portion and a gearshift position in a second gearshift portion, respectively. The main shaft includes an outer shaft portion that extends from the crankcase and supports the first and second gearshift clutches. The outer shaft portion is supported by a bearing portion disposed in a front cover on a side opposite to the crankcase across the first and second gearshift clutches.

Abstract: A lubricating device for an internal combustion engine includes an oil tank chamber defined by being separated from a crank chamber by a partition wall that is formed between a crankcase and a crankcase cover of the internal combustion engine. Oil pumped by a scavenge pump is supplied to a tank supply port which is open at an upper portion of the oil tank chamber to the oil tank chamber. The oil stored in the oil tank chamber is sucked from a feed suction port which is open at a lower portion of the oil tank chamber to be supplied to respective regions for lubrication of the internal combustion engine by a feed pump. An oil passage penetrating inside the oil tank chamber is formed below the tank supply port at an upper portion of the oil tank chamber.

Abstract: A lubricating device for an internal combustion engine includes an oil tank chamber defined by being separated from a crank chamber by a partition wall that is formed between a crankcase and a crankcase cover of the internal combustion engine. Oil pumped by a scavenge pump is supplied to a tank supply port which is open at an upper portion of the oil tank chamber to the oil tank chamber. The oil stored in the oil tank chamber is sucked from a feed suction port which is open at a lower portion of the oil tank chamber to be supplied to respective regions for lubrication of the internal combustion engine by a feed pump. An oil passage penetrating inside the oil tank chamber is formed below the tank supply port at an upper portion of the oil tank chamber.

Abstract: A small center distance is provided between a crankshaft and a gearshift shaft disposed in parallel. A power unit is built compactly in a direction of arrangement of the crankshaft and the gearshift shaft for supporting reliably the gearshift shaft on which heavy, first and second gearshift clutches are supported. A transmission includes a main shaft, disposed in parallel with a crankshaft and rotatably supported in a crankcase, and first and second gearshift clutches. The first and second gearshift clutches change a gearshift position in a first gearshift portion and a gearshift position in a second gearshift portion, respectively. The main shaft includes an outer shaft portion that extends from the crankcase and supports the first and second gearshift clutches. The outer shaft portion is supported by a bearing portion disposed in a front cover on a side opposite to the crankcase across the first and second gearshift clutches.

Abstract: A lubricating system for an internal combustion engine includes lubricating oil recovery oil passages through which lubricating oil dropping to and dwelling in a bottom portion of a crankcase after lubricating individual portions of an internal combustion engine is fed to a lubricating oil tank through an oil cooler by a recovery pump. Lubricating oil supply oil passages supply the lubricating oil from the lubricating oil tank to the individual portions of the internal combustion engine needing lubrication and cooling through an oil filter by a supply pump. The lubricating system includes a branch passage branched from the lubricating oil recovery oil passage communicating from the oil cooler to the lubricating oil tank. The branch passage supplies the lubricating oil to at least one of the individual portions of the internal combustion engine.

Abstract: An air cleaner device 41 which includes a main air cleaner 56 and a sub air cleaner 67 which is connected to the main air cleaner 56, and the sub air cleaner 67 is arranged parallel to the main air cleaner 56 in the longitudinal direction of main frames 55. In this arrangement, the air cleaner device does not projected sideward from a vehicle body and hence, the interference of the air cleaner device with an occupant and lowering of aesthetic appearance of a vehicle can be prevented. Further, since there is no restriction imposed by the interference of the air cleaner device with an occupant and lowering of aesthetic appearance of the vehicle, a capacity of air cleaner device can be easily ensured.

Abstract: An air cleaner device 41 which includes a main air cleaner 56 and a sub air cleaner 67 which is connected to the main air cleaner 56, and the sub air cleaner 67 is arranged parallel to the main air cleaner 56 in the longitudinal direction of main frames 55. In this arrangement, the air cleaner device does not projected sideward from a vehicle body and hence, the interference of the air cleaner device with an occupant and lowering of aesthetic appearance of a vehicle can be prevented. Further, since there is no restriction imposed by the interference of the air cleaner device with an occupant and lowering of aesthetic appearance of the vehicle, a capacity of air cleaner device can be easily ensured.

Abstract: A lubricating system for an internal combustion engine includes lubricating oil recovery oil passages through which lubricating oil dropping to and dwelling in a bottom portion of a crankcase after lubricating individual portions of an internal combustion engine is fed to a lubricating oil tank through an oil cooler by a recovery pump. Lubricating oil supply oil passages supply the lubricating oil from the lubricating oil tank to the individual portions of the internal combustion engine needing lubrication and cooling through an oil filter by a supply pump. The lubricating system includes a branch passage branched from the lubricating oil recovery oil passage communicating from the oil cooler to the lubricating oil tank. The branch passage supplies the lubricating oil to at least one of the individual portions of the internal combustion engine.

Abstract: To improve a mounting configuration for a chain guide of a cam chain for transmitting power to a power system of an internal combustion engine to make mounting of a chain guide and a cylinder block simple and easy. A mounting device for a cam chain guide for an internal combustion engines constructed such that rotation of a crank shaft is transmitted to a cam shaft provided externally of a cylinder bore by a cam chain 3 to operate an intake/exhaust valve through a push rod and a rocker arm. A first protrusion provided in the vicinity of a lower end of a chain guide is fitted into a first locating groove provided in the vicinity of a crank shaft of a crank casing, and a second protrusion provided in the vicinity of an upper end of a chain guide is fitted into a second locating groove provided in a lower surface of a cylinder block and gradually enlarged from a protrusion fixed position toward an opening.

Abstract: An oil separating chamber for separating oil contained in blow-by gas is arranged outside a transmission member passage connecting a crank shaft with a cam shaft of a valve system and at an abutting surface between a cylinder block and a cylinder head. Partition walls perpendicular to the abutting surface for dividing the oil separating chamber into a plurality of small subchambers are alternatively arranged at the cylinder block and the cylinder head to form a labyrinth structure. The small subchamber at one end of the plurality of small subchambers is provided with a blow-by gas intake passage communicated with the transmission member passage. The small subchamber at the other end is provided with a blow-by gas exhaust passage for returning blow-by gas to an air cleaner. Each of the small subchambers not provided with the blow-by gas intake passage is provided with an oil return passage communicating with the transmission member passage.

Abstract: An oil separating chamber for separating oil contained in blow-by gas is arranged outside a transmission member passage connecting a crank shaft with a cam shaft of a valve system and at an abutting surface between a cylinder block and a cylinder head. Partition walls perpendicular to the abutting surface for dividing the oil separating chamber into a plurality of small subchambers are alternatively arranged at the cylinder block and the cylinder head to form a labyrinth structure. The small subchamber at one end of the plurality of small subchambers is provided with a blow-by gas intake passage communicated with the transmission member passage. The small subchamber at the other end is provided with a blow-by gas exhaust passage for returning blow-by gas to an air cleaner. Each of the small subchambers not provided with the blow-by gas intake passage is provided with an oil return passage communicating with the transmission member passage.

Abstract: To improve a mounting configuration for a chain guide of a cam chain for transmitting power to a power system of an internal combustion engine to make mounting of a chain guide and a cylinder block simple and easy. A mounting device for a cam chain guide for an internal combustion engine is constructed such that rotation of a crank shaft is transmitted to a cam shaft provided externally of a cylinder bore by a cam chain 3 to operate an intake/exhaust valve through a push rod and a rocker arm. A first protrusion provided in the vicinity of a lower end of a chain guide is fitted into a first locating groove provided in the vicinity of a crank shaft of a crank casing, and a second protrusion provided in the vicinity of a lower end of a chain guide is fitted into a second locating groove provided in a lower surface of a cylinder block and gradually enlarged from a protrusion fixed position toward an opening.

Abstract: An overhead valve type internal combustion engine having a breather chamber without increasing the size of the internal combustion engine by taking advantage of a space that is already formed. An overhead valve type internal combustion engine includes a cylinder bore formed in a cylinder, a freely rotatable cam shaft located in a cylinder head, and also located to the side of the cylinder bore viewed from a direction of a centerline of the cylinder, a chain chamber, located to the side of the cylinder bore, for housing a chain for rotationally driving the cam shaft, and a breather chamber located so as to be below the cam shaft and parallel to the cylinder bore on one side of the chain chamber.